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Question

到達詞典列表內的字典我有一個dictionary，看起來像這樣：

{'items': [{'id': 1}, {'id': 2}, {'id': 3}]} 

，我正在尋找一種方式來直接訪問內部字典，id = 1。

有沒有辦法達到此目的而不是循環list項目和比較id？

Answer 1

first_with_id_or_none = \ 
    next((value for value in dictionary['items'] if value['id'] == 1), None) 

Answer 2

您將有通過列表循環。好消息是，是，你可以使用一個發電機表達next()做循環：

yourdict = next(d for d in somedict['items'] if d['id'] == 1) 

這可以養StopIteration異常，如果沒有這樣的匹配字典。

使用

yourdict = next((d for d in somedict['items'] if d['id'] == 1), None) 

返回缺省的，而不是針對邊緣的情況下（這裏使用None，但挑你的需要）。

Answer 3

使之成爲一個功能：

def get_inner_dict_with_value(D, key, value): 
    for k, v in D.items(): 
     for d in v: 
      if d.get(key) == value: 
       return d 
     else: 
      raise ValueError('the dictionary was not found') 

並提供瞭解釋：

def get_inner_dict_with_value(D, key, value): 
    for k, v in D.items(): # loop the dictionary 
     # k = 'items' 
     # v = [{'id': 1}, {'id': 2}, {'id': 3}] 
     for d in v: # gets each inner dictionary 
      if d.get(key) == value: # find what you look for 
       return d # return it 
     else: # none of the inner dictionaries had what you wanted 
      raise ValueError('the dictionary was not found') # oh no! 

運行它：

>>> get_inner_dict_with_value({'items': [{'id': 1}, {'id': 2}, {'id': 3}]}, 'id', 1) 
{'id': 1} 

---

另一種方法：

def get_inner_dict_with_value2(D, key, value): 
    try: 
     return next((d for l in D.values() for d in l if d.get(key) == value)) 
    except StopIteration: 
     raise ValueError('the dictionary was not found') 

>>> get_inner_dict_with_value2({'items': [{'id': 1}, {'id': 2}, {'id': 3}]}, 'id', 1) 
{'id': 1}